Thermal relay



May 31, 1949.

J. D. BOLESKY THERMAL RELAY 3 Sheets-Sheet 1 Filed July 10, 1943 y 1949-J. D. BOLESKY 2,471,924

THERMAL RELAY Filed July- 10, 1943 3 She'ets-Sheat 2 y 1949. J. D.BOLESKY I 2 471 924 THERMAL RELAY Filed July 10, 3 Sheets-Sheet S k 26a7 32 2/ 47 5/ f3 .35 H I 59 /7 l i Patented May 31, 1949 THERMAL RELAYJohn D. Bolesky, Attleboro, Mass., assignor to Metals 6; ControlsCorporation,

Attleboro,

Mass, a corporation of Massachusetts Application July 10, 1943, SerialNo. 494,173

Claims. (Cl. 6023) This invention relatesto thermal relays, and morespecifically to an ambiently compensated thermostatic relay mechanism.

Among the several objects of the invention may be noted the provision ofa simple and reliable snap-acting thermal relay mechanism which has aquick response from a remote control; the provision of apparatus of theclass described in which no current flows except during relatively shortperiods; and the provision of apparatus of this class which iscompensated for changes in ambient temperature. Other objects will be inpart obvious and in part pointed out hereinafter.

The invention accordingly comprises the elements and combinations ofelements, features oi. construction; and arrangements of parts whichwill be exemplified in the structures hereinafter described, and thescope of the application of which will be indicated in the followingclaims.

In the accompanying drawings, in which are illustrated several ofvarious possible embodiments of the invention,

Fig. l is a view in elevation showing certain mechanical parts in oneposition, wiring being omitted;

Fig. 2 is a top plan view of Fig. 1;

Fig. 3 is a vertical section taken on line 3-3 of Fig. 2, but showingthe parts in an alternate position;

Fig. 4 is a wiring diagram with parts according to their position shownin Fig. 1;

Fig. 5 is a wiring diagram with parts according to their position shownin Fig. 3;

Fig. 6 is a wiring diagram showing an alternative form of the invention;and,

Fig. 7 is a wiring diagram showing still another form of the invention.

Similar reference characters indicate corresponding parts throughout theseveral views of the drawings.

Referring now more particularly to Fig. 1, there is shown in general atnumeral I a thermostatic relay unit. At numerals 3 are shown electricalinsulating and heat resistant plates held together spacedly by spacingpillars 5 and 1, these being clamped together by studs 9 (see also Figs.2 and 5).

The lower pillars 1 are grooved as shown at l l for loosely holdingedges of thermostatic snapacting plates in the form of discs 43 and i5.These discs are what are known to the art as Spencer discs, eachpreferably consisting of a bimetallic snap-acting curved sheet. Theupper disc I3 has its metal of high coeflicient of expansion H on theupper side and the metal of low coefllcient of expansion L on its lowerside. The lower disc l5 has its metal of high coeillcient of expansionon the lower side and its metal of low coeilicient of expansion on theupper side. Thus the metals L are adjacent to one another and inside ofthe pair of discs, and the metals H are outside.

Centrally, the discs are provided with openings for loose reception ingrooves l6 of a spacing pillar l1. Through pillar I1 is threaded a stemI! held in place by a lock nut l8. Stem l! carries at its top 20 aninsulating bar 2 I. At its top .he stem is square 50 as to be guidedwithout rotation in a square opening 23 in the middle plate 3.

The bar 2i is a switch actuating means. The switches operated therebyare carried on the upper insulating plate 3. These switches compriseterminals 25 and 26, from which extend cantilever springs 21 and 29respectively. These springs carry at their ends movable contacts 3i and32 respectively. The movable contact 32 of the spring 29 is normallybiased downward to touch a fixed contact 31 carried on an underslungbracket 35 (Fig. 5). The movable contact II at the end of the spring 21is engageable with a fixed contact 33, but normally stands in downwardlyspaced relation to said contact 33 (Fig. 5). The contact 33 is wired toa lower heater coil M held on suitable insulating brackets on the lowerplate 3, the other end of this coil 4| connecting with a line wire 53 at45, as shown in Fig. 5. The contact 37 is wired into an upper heater Msupported under the middle plate 8. The other end of the heater 4! isconnected to said circuit 53, as shown in Fig. 5.

The terminals 25 and 26 are respectively con" nected to terminals 49 and50 of a single-pole double-throw switch 5 l the single pole of which isconnected to the other side of the energizing circuit 53.

The upper heater 41 'is adjacent to the highexpansion side (outside) ofthe upper disc l3 and the lower heater ii is adjacent the high-expansionside (outside) of lower disc l5. Thus the discs are respectivelyexteriorly heated by the respectively adjacent heaters.

The two thermostatic discs l3 and I5 have the same strength andtemperature-operating characteristics, but they are oppositely operativein response to a given temperature change, becauseof the oppositelocation of the metals of high and low coeillcients of expansion. Thediscs being coupled in tandem and located parallel to one another, whenheated to the same temperature (as would be the case were they both inthe same ambient heating medium),v there will be noactivity of the discsfrom a given position, such as shown in Fig. 4 or 5. That is to say, thepair of discs I3 and I may be placed either in the position shown inFig. 4, or in the position shown in Fig. 5, and change in the ambienttemperature will cause no activity of the discs.

It the upper heater 41 alone is heated sufllciently in the Fig. 5position, then the discs I3 and I5 will snap from the positions shown inFigs. 3 and 5 to the upward positions shown in Figs. 1 and 4 and remainthere even though the disc temperatures later equalize. If only thelower heater ll is heated in the Fig. 4 position, then the discs willsnap from their upward positions shown in Figs. 1 and 4 to the downwardpositions shown in Figs. 3 and 5 and remain there even though the disctemperatures later equalize. The discs will retain a given up or downposition which is stable at any value of ambient temperature around themas long as it is -sub-. stantially the same for both discs, for reasonsgiven in United States Patent 2,203,558 (refer to Figs. 5 and 6 andaccompanying description therein).

Operation is as follows, referring to Figs. 4 and 5:

The parts are stable in the Fig. 5 position. To operate, the selectivecontrol switch 5i is thrown over to the dotted-line position, that is,on point 50. This sends current through the thenclosed switch contacts32, 31, heater t? and back to the line 53. The heater 4? heats the upperdisc I3, and since the metal of high coeflicient of expansion is on top,the disc snaps up from the position shown in Fig. 5 to that shown inFig. 4 (carrying along disc I5). Both discs then permanently hold theFig. 4 position, even after the upper disc I3 cools down to thetemperature of lower disc I5. This cooling will of course occur, sincewhen the device moves from the Fig. 5 to the Fig. 4 position, thecontacts 32, 3'8 are opened and the heater All is deenergized.

The above closes switch contacts 3i and 33 (Fig. 4), but since thecontrol switch Si is at this time on point 50, as indicated by the solidline in Fig. 4, no current is available for either heater I or 41.

Now, if the control switch 5! be thrown from its solid-line to itsdotted-line position (Fig. 4) to point 49, current will flow throughcontacts II, 33, lower heater II, and back to the line 53. This heatsthe lower disc I5, and since its metal of high coeflicient of expansionis below, this disc will snap down, carrying along with it the upperdisc I3. This opens contacts 39, 33 and recloses the contacts 32, 3? asshown in Fig. 5. Since switch 5I is on point 49 all circuits are againbroken through the heaters, and the parts maintain the Fig. 5 positionuntil the switch 5| is again thrown to point 5Il.

The member I9 has a downward extension which is attached to means whichit is desired to operate, such as for example an electric switch, valveor the like.

It will be seen that the invention provides a thermal relay which has aquick-acting forceful response. The metals H of high coemcient ofexpansion of the tandem discs I3 and I5 being -on the outside of theassembly of discs and the temperature with some delay caused by the timethat it takes for heat to be transmitted through the outside component.Thus, the design is particularly eflective to bring about a quick andpositive action.

Between operations no current is consumed, switch 5| being normallyclosed in connection with whichever oi the pairs of contacts 3|, 33 or:2. :1 is open.

As shown in Fig. 7 the heaters 41 and 4| may be dispensed with if it isdesired to use the discs I3 and I5 per se as heating units. In such casethe discs. will be made of material presenting proper electricalresistance to generate the required amount of heat for self -operation;or selfoperating current-conducting discs may be used with auxiliaryheaters. Self-operated currentcarrying discs are shown in the patent toVaughan et al. 2,207,422; and discs with auxiliary heaters are shown inmy Patents 2,199,387 and 2,199,388.

The application of the circuit connections for v causing the discs togenerate heat for self-enerinclude the respective discs I5 and I3, with(Fig.-

gization will be clear from said patents and from Figs. 6 and '7. I Thusthe parallel circuit branches through the automatic switches 21 and 29,may

6) or without (Fig. 7) the heaters 4| and 41. In Fig. 6 the disc I I isconnected in shunt around heater 4'! by lines 53 and GI. The disc I5 iscon nected in shunt around heater II by lines 55 and 51. In Fig. '7discs I3 and I5 are connected in their respective circuits by lines 59and GI, and

55 and 51, but heaters 4| and 41 are omitted. Discs I3 and I5 thereforein both embodiments carry the current in their respective circuits andthemselves serve as a heating means.

In View of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

As many changes could be made in the above 4 constructions withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

I claim:

1. A thermal relay comprising an ambienttemperature-compensatedthermostatic means embodying two inherently snap-acting thermo staticplates arranged so that snap movement of one opposes snap movement ofthe other, said plates being coupled for conjoint snap movement, a firstelectrical heating circuit including a first switch for heating one ofsaid plates to snap both plates from a first position to a secondposition, a second electrical heating circuit including a second switchfor heating the other plate to snap both plates i'rom their secondposition to their first position, and switch actuating means controlledby said thermostatic means adapted in the first position of said platesto close the first switch and open the second switch, and in the secondposition of said plates to close the second switch and open the firstswitch.

2. A thermal relay comprising an ambienttemperature-compensatedthermostatic means embodying two inherently snap-acting thermostaticplates arranged so that snap movement of one opposes snap movement ofthe other, said plates being coupled for conjoint snap movement, a firstcircuit including a first switch and a first electrical heating elementin heat-exchange relation to one of said plates for heating said oneplate to snap both plates from a first position to a second position, asecond circuit including a second switch and a second electrical heatingelement in heat-exchange relation to the other plate for heating it tosnap both plates from their second to their first position, and switchactuating means controlled by said thermostatic means adapted in thefirst position of said plates to close the first switch and open thesecond switch, and in the second position of said plates to close thesecond switch and open the first switch.

3. A thermal relay comprising an ambienttemperature-compensatedthermostatic means embodying two inherently snap-acting thermostaticplates arranged so that snap movement of one opposes snap movement ofthe other, said plates being coupled for conjoint snap movement, a firstelectrical heating circuit including a first switch and also includingone of said plates as an electrical resistance heating element forheating said one plate to snap both plates from a first position to asecond position, a second electrical heating circuit including a secondswitch and also including the other of said plates as an electricalresistance heating element for heating said other plate to snap bothplates from their second to their first position, and switch actuatingmeans controlled by said thermostatic means adapted in the firstposition of said plates to close the first switch and open the secondswitch, and in the second position of said plates to close the secondswitch and open the first switch.

4. A thermal relay comprising an ambienttemperature-compensatedthermostatic means embodying two coaxial and parallel inherentlysnap-acting thermostatic bimetal dished discs coupled for conjoint snapmovement with their respective low coefiicient of expansion sidesadjacent one another. whereby snap movement of one disc opposes snapmovement of the other, a first electrical resistance heating elementadjacent the high expansion side of one disc for heatingsaid one disc tosnap both discs from a first to a second position, said element beingconnected in a first circuit including a first switch, a secondelectrical resistance heating element adjacent the high expansion sideof the other disc for heating said other disc to snap both discsfromtheir second to their first position, said second heating element beingconnected in a second circuit including a second switch, and switchactuating means controlled by said thermostatic means adapted in thefirst position of said discs to close the first switch and open, thesecond switch, and in the second position or said discs to close thesecond switch and open the first switch.

5. A thermal relay comprising a support including a pair of spacedinsulation plates held together by spacing members, a pair of snapactingthermostat bimetal dished discs edgemounted in grooves in the spacingmembers between the plates, said discs being mounted in coaxial spacedrelation with their low coefficient of expansion sides facing oneanother, a stem centrally connecting the discs for conjoint snapmovement, one end of the stem extending through an aperture in one ofthe plates and carrying a switch actuating member outward of the plate,a first electrical resistance heating element carried 6 by one of theplates in heat-exchange relation to the high coefiicient side of thedisc adiacent that plate for heating said disc to snap both discs to afirst position bowed toward said first heating element, a secondelectrical resistance heating element carried by the other plate inheat-exchange relation to the high coefilcient of expansion side of theother disc for heating said other disc to snap both discs to a secondposition bowed toward said second heating element, first and secondswitches carried by the support in P0511 tion for actuation by theswitch-actuating member, the first switch being connected in a firstcircuit in series with the first heating element. the second switchbeing connected in a second circuit in series with the second heatingelement, said switch actuating member closing the first switch andopening the second switch in the first position of the discs, andclosing the second switch and opening the first switch in the secondposition of the discs. 5

6. A thermal relay as-set forth in claim 1, turther'including a powersupply circuit having a double-throw control switch adapted selectivelyto energize one or the other of said first and second heating circuits.

7. A thermal relay as set forth in claim 2, fur- I ther including apower supply circuit having a double-throw control switch adaptedselectively to energize one or the other of said first and secondcircuits.

8. A thermal relay as set forth in claim 3, further including a powersupply circuit having a double-throw control switch adapted selectivelyto energize one or the other of said first and second heating circuits.

9. A thermal relay as set forth in claim 4, further including a powersupply circuit having a double-throw control switch adapted selectivelyto energize one or the other of said first and second circuits.

10. A thermal relay as set forth in claim 5, further including a powersupply circuit having a double-throw control switch adapted selectivelyto energize one or the other of said first and secand circuits.

JOHN D. BOLESKY.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

